In the treatment of carious lesions the major part of the carious tissue can be examined by judging the hardness of the affected surface using tactile instruments (so-called probing) and/or by visually observing the well known discoloration known as Maillard products. However, the caries affected surface near the healthy dentin, which is called the transparent zone, is not discoloured.
For early stage caries where the caries only affects the enamel of the tooth different therapies are used. In one therapy one removes the caries affected tissue using mechanical means such as dental drill tools. Another therapy uses a preventive methodology such as fluoridation.
Initial caries, i.e. caries affecting only the enamel of the tooth, is normally detectable for the dentist as a diminished translucence in areas of caries, and can be observed as an opaque area due to the porous enamel. However, detection of caries in the inter proximal area between teeth requires radiographic analysis.
In all situations it might not be possible to remove all carious tissue. For instance, this may be the case when the carious lesions have progressed into the dentin of the tooth. Some carious dentin tissue may then still remain and this carious tissue may become locked in underneath a filling used to repair the tooth. This will certainly cause further development of carious dentin tissue, which can develop unseen due to the fact that it is hidden underneath the filling. When the affected individual becomes aware of the carious dentin tissue it might be hard to save the tooth, and extraction or root filling may be needed.
This problem can of course be handled by excavating more healthy dentin tissue from the tooth; i.e. healthy dentin tissue will be removed in addition to the carious dentin tissue. However, this will lead to a weakening of the tooth strength (i.e. less crystals, hydroxyapatite, and less proteins, respectively), and the crown walls may become too thin. Further this will lead to a decrease in the tooth re-mineralisation process since tissue is replaced by a synthetic material like a composite. Taking away tissue affects the whole tooth, both the inorganic and the organic parts.
US 2007/0287122 describes a method of treating residual caries comprising the steps of a) flushing carious tissue with a stain chosen to readily absorb energy from a chosen laser source, b) allowing some of the stain to be absorbed by the carious tissue; c) rinsing the area, leaving the absorbed stain in the carious tissue; and d) removing carious tissue with ablation by laser of a complimentary wavelength and subsequent etching of remaining inorganic tissue using an acid.
WO 2008/048170 discloses a method for determining the presence of carious dentin tissue by means of infrared spectroscopy, which is based on the finding that ester groups are present in carious tissue in contrast to healthy dentin tissue that lacks ester groups.
WO 98/020838 describes a preparation for chemical-mechanical treatment of carious tissue in the form of a two-component caries-dissolving liquid including a coloring agent such as Erythrosin.
WO 2007/123880 discloses a method and a kit for early stage caries detection wherein the early dental caries may be detected by binding an optically detectable probe such as Hylight Fluor to the enamel caries an using an optical device for detection. Nothing is mentioned about detection of dental caries that has progressed into the dentin tissue; i.e. carious dentin tissue.
It is well known in the art that healthy dentin tissue comprises amide groups. This is described in, for instance, Digestion and Nutrition: In Zoology by Dorit, I L R. and Walker, W. F, Saunders College, page 247 as well as in Primary Structure Determination In Biochemistry by Voet, D. and Voet, G. E., 2nd edition, John Wiley & Sons, Inc. NY, at page 156.
Accordingly, there is a need for devices and methods allowing for detection and removal of a maximum of carious dentin tissue without affecting or affecting very little of healthy dentin tissue.